JP2009502586A - Process for producing extruded composition of extruded die and filled polymer composition - Google Patents

Abstract

Prepare an extruded filled polymer composite having a highly disperse and uniformly distributed filler by extruding a filled polymer composite through a die with a Flow Restriction Zone, a Flow Redistribution Zone and a Land Zone. The Flow Restriction Zone is proximate to the extruder and increases polymer melt backpressure in the extruder sufficient to induce high dispersion of the filler but not enough to cause undesirable degradation of the polymer melt components.

Description

  The present invention relates to an extrusion die that includes a flow restriction zone, a flow redistribution zone, and a land zone. The present invention also relates to a method of using the extrusion die to prepare a filled polymer composition extrudate comprising a highly dispersed and uniformly distributed filler.

  Dispersing fillers in a polymer matrix has historically been challenging, especially when the filler and polymer are not particularly compatible. The challenge increases as the amount of filler increases relative to the matrix material and as product requirements seek a highly uniform composition. Manufacturing extrudates of compositions comprising hydrophilic filler dispersed in a hydrophobic polymer suffers from such challenges because the filler and polymer are not particularly compatible. The challenge is more difficult when the filler and / or matrix material has a tendency to be degraded by heat, as in the case of cellulose fillers. Manufacturing extrudates of compositions with wood fillers in a thermoplastic matrix is very difficult (eg, US Pat. No. 5,851,469, column 1, lines 52-2). Column 25th line).

  Despite being difficult to manufacture, composite extrusions made of thermoplastic polymer matrix mixed with wood particles (wood flour / plastic compound) can be used for all applications such as deck materials (eg, boards and handrails). Is a desirable alternative to wood boards. Wood flour / plastic compositions require less wood material per unit volume, can use lower grade wood materials (including recycled and waste wood materials), and more than all wood substitutes Can have a long useful life.

  Wood flour / plastic composition extrudates are commercially available. However, the product and literature indicate that there remains a need for wood flour / plastic compositions in which wood flour fillers are highly dispersed and uniformly distributed, and an efficient method for producing such compositions. Show.

  U.S. Pat. No. 4,708,623 teaches that conventional single and twin screw extruder screw designs are inadequate to disperse wood flour fillers in a polymer matrix. An unconventional screw zone is disclosed for the purpose of unraveling the fibers. U.S. Pat. No. 4,708,623 discloses the use of a multi-orifice base (strand plate) to extrude pellets of encapsulated wood flour filler and then remanufacture those pellets into molded articles. In view of the weld lines identified in U.S. Pat. No. 5,516,472 (see below), those skilled in the art will recognize that the pellets of U.S. Pat. No. 4,708,623 extruded through a strand plate are uneven distribution of filler. Would expect to have Furthermore, the method of extruding the filled polymer composition into pellets, followed by subsequent molding of the composition pellets into an article is undesirably a single step of compounding and extruding the composition into an article in a single step. Less efficient than the law.

  US Pat. No. 5,516,472 and related family members teach a method of dispersing and distributing wood flour fillers in a thermoplastic matrix using a strand method that requires extrusion through a strand die. is doing. However, the strand method of US Pat. No. 5,516,472 produces a weld line in the extruded product, which sees the flattened surface of the extruded product perpendicular (end-on) to the extrusion direction of the product. It is clear. Presumably, the weld line is a polymer-rich skin around each strand, which results in a heterogeneous dispersion on the strand surface. As a result, when flattened, the product of US Pat. No. 5,516,472 suffers from an inhomogeneous side-by-side appearance. Rumors also indicate that the extruded product of US Pat. No. 5,516,472 also suffers from hygroscopic problems along the longitudinal flow path (US Pat. No. 6,153,293, column 3, lines 65-4). Column 6th line).

  Another way of facilitating mixing of the filler into the extruded polymer composition is to use a die with a compression ratio of at least 3: 1. Increasing the compression ratio can also increase the flexural modulus of the extruded product containing the filler. The compression ratio is the ratio of the widest cross-sectional area of the base to the cross-sectional area of the outlet orifice of the base. A die having a 3: 1 compression ratio requires a die channel having a cross-sectional area that is at least three times the cross-sectional area of the outlet orifice of the die (ie, approximately that of the extruded product). Unfortunately, a die that produces a compression ratio of at least 3: 1 can be inconveniently large when designed to produce a product with a large cross-sectional area. In addition, or as an alternative, enhancing mixing by increasing the compression ratio of the die requires cooling the polymer composition to obtain a high melt viscosity within the die, which is the final extruded product Tend to hinder achieving a high quality surface appearance.

US Pat. No. 5,851,469 US Pat. No. 4,708,623 US Pat. No. 5,516,472 US Pat. No. 6,153,293

  An efficient method of preparing a filled polymer composition, particularly a composition filled with talc or wood flour, comprising a highly dispersed and uniformly distributed filler, especially talc or wood flour filler, is desired. . More desirable is a method that allows the use of a conventional extruder without the need for a strand die or a compression ratio of at least 3: 1.

  The present invention relates to an extrusion port suitable for efficiently producing a filled polymer composition comprising a wood powder filler that is highly dispersed and uniformly distributed in a polymer matrix directly from an extruder. Advances technology by providing a method using gold and its caps.

In a first aspect, the present invention provides an extrusion die that defines a die flow channel,
(A) Flow Restriction Zone that defines a restrictive flow channel (Restrictive Flow Channel) extending from the inlet orifice to the outlet orifice at the opposite end of the flow restricting zone. An exit orifice having a cross-sectional area equal to the smallest cross-sectional area of the flow path, and (ii) an average cross-sectional area less than the circumferential area at the restrictive flow path inlet end).
(B) A flow redistribution zone that defines a redistribution flow channel extending from an inlet orifice adjacent to the outlet orifice of the restrictive channel to an outlet orifice at the opposite end of the flow redistribution zone (however, The redistribution flow path is in fluid communication with the restrictive flow path and first increases in cross-sectional area from the cross-sectional area of the restrictive flow path exit orifice.), And (c) adjacent to the redistribution flow path exit orifice. Land Zone that defines a Land Flow Channel that extends from the inlet orifice to the outlet orifice at the opposite end of the land zone (however, the land channel is in fluid communication with the redistribution channel and (The variation in the dimensions of any cross section at any two points between the inlet and outlet ends of the zone is less than 5%.)
Including
The restrictive flow path has a smaller average cross-sectional area than the redistribution flow path or the land flow path, the combination of the restrictive flow path, the redistribution flow path and the land flow path defines the base flow path, and the base flow path Provides a laminar flow of polymer melt throughout the die from the inlet end of the die defining the restrictive flow path and die inlet orifice to the opposite outlet end defining the land flow channel and die outlet orifice. .

  In a second aspect, the present invention is a method of extruding a filled polymer composition comprising extruding a composition comprising a polymer and a filler from an extruder through an extrusion die, wherein the extrusion die is It is the extrusion die of the first aspect.

Extrusion Base The base of the present invention has three zones: (a) a flow restricted zone (“Band (a)”), (b) a flow redistribution zone (“Band (b)”), and (c) a land. Band (“band (c)”).

  Each zone defines a flow path (conduit) that extends throughout the zone (ie, from one end of the zone (inlet end) to the opposite end (outlet end)). Each channel allows laminar flow of polymer melt in the zone. “Polymer melt” refers to a material that is finally extruded from a die and includes a softened polymer and additives (including fillers) that may be present in the polymer. Laminar flow means that there is no “dead point” where the molecular flow stops or changes direction by more than 90 degrees. Dead center typically arises from a barrier extending perpendicular to the polymer melt stream. The band of the base is zone (b) between zones (a) and (c), the inlet end of zone (b) is adjacent to the outlet end of zone (a), and the inlet of zone (c) They are aligned with each other so that the ends are adjacent to the exit end of zone (b). The flow paths in each zone are in fluid communication with each other and are preferably coaxial with each other.

  Channels that pass through zone (a) (“restrictive channel”), zone (b) (“redistribution channel”) and zone (c) (“land channel”) They are aligned to form. The base passage extends from the inlet end of the base (the inlet end of the base is also the inlet end of the zone (a)) to the outlet end of the base (the outlet end of the base is also the outlet end of the zone (c)). ing. The die channel provides a laminar flow to the polymer melt throughout the die. The polymer melt enters the base channel through the inlet orifice at the inlet end of the base and exits the base channel through the outlet orifice at the outlet end of the base. In a preferred embodiment, the mouth channel can only enter and exit through the inlet and outlet orifices.

  The base may have a single structure or a modular structure. Modular means having components that are separable from each other. For example, band (a) may be separable from bands (b) and (c). Band (c) may be separable from bands (a) and (b). Each band may be separable from each other band. Removable (modular) components within each band that are present in a single band that spans more than one band or in combination with other components that span more than one band May be included. Modular bases are desirable because they allow easy and low cost modification of the base. For example, a craftsman may want the base to have a more or less restrictive flow in zone (a) in order to optimize product properties for a particular formulation. Rather than creating a completely new base (ie, each of zones (a), (b), and (c)), craftsmen who use a modular base will simply restrict flow in zone (a). A modular component or a plurality of components that control the process can be redesigned and manufactured, and then the original component can be replaced with the redesigned component. Modular bases can save time and money when making manufacturing changes.

  The base is attached to the extruder at the inlet end of zone (a) adjacent to the extruder. The present invention contemplates that there are numerous ways of attaching the die to the extruder and that the present invention is not limited to any particular attachment means.

  The polymer melt exits the extruder through the exit orifice of the extruder and enters the die through the inlet orifice of the die. Desirably, the inlet orifice to the flow restricting channel has a circumferential profile similar to the outlet orifice of the extruder to which the die is attached. The perimeter contour defines the shape and dimensions of the orifice. The exit orifice of the extruder and the inlet orifice of the base desirably have similar peripheral contours, preferably the same peripheral contour. However, as long as they provide a laminar flow of polymer melt from the outlet orifice of the extruder through the inlet orifice of the extruder, the outlet orifice of the extruder and the inlet orifice of the base need not be the same.

Zone (a)-Flow Restriction Zone Zone (a) defines a restrictive flow path spanning the length of zone (a) beginning at the inlet orifice and ending at the outlet orifice. Zone (a) extends from the inlet end of the die to where the cross-sectional area of the die channel increases from its smallest cross-sectional area. Thus, the outlet orifice of the restrictive flow path has a cross-sectional area equal to the smallest cross-sectional area of the mouthpiece flow path.

  The purpose of zone (a) is to achieve the desired dispersion of the filler in the polymer melt while avoiding sufficient back pressure to undesirably generate enough heat to degrade the polymer melt components. Is to create sufficient back pressure in the extruder to achieve this. Zone (a) increases the back pressure in the extruder by restricting the polymer melt flow through the restrictive flow path. The flow parameters in zone (a) control the restriction of the polymer melt flow through the restrictive flow path. For example, increasing the length of the restrictive flow path in zone (a) or decreasing the average cross-sectional area will increase the restriction of polymer melt flow through zone (a). One skilled in the art can empirically select the proper flow parameters for zone (a) to achieve optimal mixing with minimal degradation based on the particular polymer melt formulation.

  Desirably, zone (a) restricts the polymer melt flow with a restrictive flow path having an average cross-sectional area that is smaller than the peripheral area of the inlet orifice to the restrictive flow path. The “peripheral area” is an area surrounded by the periphery. In this particular case, the perimeter area of the inlet orifice to the restrictive flow path is the area within the perimeter of the restrictive flow path measured in a cross section perpendicular to the polymer melt flow. The average cross-sectional area of the restrictive flow path is also smaller than the average cross-sectional area of the redistribution flow path in zone (b) and the land flow path in zone (c).

  Here, the cross-sectional area of the orifice or flow path is the open space area in a cross section perpendicular to the polymer melt flow in the orifice or flow path (for example, the space through which the polymer melt can flow). Say. The average cross-sectional area of the channel is determined by dividing its open space volume by its length (the distance from one end to the opposite end through the center of the channel). It should be noted that the orifice or cross-section can have a “cross-sectional area” that is smaller than the “peripheral area”. This is because the peripheral area is a measurement of the area in the periphery of the orifice, whereas the cross-sectional area is a measurement of only free space in the peripheral area. For example, a flow path that includes a static mixer baffle will have a cross-sectional area that is less than the surrounding area.

  In the first embodiment, the restrictive flow path includes first and second sections. The first section of the restrictive flow path has a cross-sectional area that decreases from the cross-sectional area of the inlet orifice to the cross-sectional area of the second section. The reduction may follow any size profile as long as the reduction provides laminar flow of the polymer melt through the restrictive flow path, e.g., the cross-sectional area increases first and then the cross-sectional area decreases. Also good. Typically, the first compartment defines a uniform and streamlined gradient up to the cross-sectional dimensions of the second compartment to facilitate laminar flow of the polymer melt. The second compartment maintains a constant cross-sectional area and has a cross-sectional area equal to the smallest cross-sectional area of any portion of the die channel. The second compartment may have a length of 1 mm or less, but typically has a length of 2 mm or more, preferably 5 mm or more, more preferably 10 mm or more. The restrictive channel ends in the second compartment, which then feeds the polymer melt to the redistribution channel.

In a second embodiment, the restrictive flow path includes one or more static mixer elements if the static mixer element allows laminar flow in the restrictive flow path. A specific example of a suitable static mixer element is the Kenics ^TM brand mixer available from Chemineer, Inc. (Kenics is a trademark of Robbins & Myers, Inc.) .) Another suitable static mixer is a Polyguard mixer (available from Sulzer Corp.). The static mixer can limit the polymer melt flow in the restrictive channel without reducing the restrictive channel cross-sectional area from the restrictive channel inlet orifice cross-sectional area.

  In the first embodiment and the second embodiment, the first compartment, the second compartment or both the first compartment and the second compartment of the first embodiment are one of the second embodiment or It can be combined to include more static mixer elements.

  If the restrictive flow path is too long, the molten polymer melt will begin to thermally degrade before it can exit the die. Therefore, it is desirable that the restrictive flow path be as short as possible. Typically, the total length of the restrictive flow path is 24 inches (61 cm) or less, preferably 16 inches (41 cm) or less, more preferably 8 inches (20 cm) or less, and most preferably 4 inches (10 cm) or less. is there. The restrictive flow path can have a length of 2 inches (5 cm) or less, and can even have a length of 1 inch (2.5 cm) or less. In order to ensure sufficient back pressure, the length of the restrictive flow path is typically at least 0.5 inches (12.5 mm).

  One desirable restrictive flow path has a circular cross section, is 1-2 inches (2.5-5 cm) in length, and has a diameter of 0.5-1.5 inches (1.3-3.8 cm). Without the static mixer element. Numeric ranges include values at both ends.

  The cross-sectional shape of the restrictive flow path is not critical, and may be, for example, circular, oval, square, rectangular, pentagonal, hexagonal, heptagonal, octagonal, star or any other conceivable shape . The cross-sectional shape of the restrictive channel may be different at different points of the restrictive channel. Desirably, the restrictive flow path has a symmetrical shape about the axis of the polymer melt flow to facilitate uniform flow rate of the polymer melt and ultimately improve the dimensional stability of the extruded product. Have Preferably, the restrictive flow path has a circular cross-sectional shape.

  It is contemplated that band (a) may exist as part of a single base unit that also includes band (b) or band (b) and band (c). Band (a) may also be modular, apart from bands (b) and (c). Zone (a) may itself contain a plurality of modular components. For example, compartment 1 may be part of one modular base component, compartment 2 may be part of another modular base component, or the static mixer may be a zone ( It may be removable from the rest of a). In such cases, zone (a) includes a combination of modular base components or includes those portions of the modular base components present in zone (a).

Zone (b)-Flow redistribution zone Zone (b) exists after zone (a) in the base and defines the flow of polymer melt from the restrictive channel by the land channel. It serves to distribute the desired final product shape. Thus, the flow path in zone (b), the redistribution flow path, has a profile suitable for distributing the polymer melt from the restrictive flow path into the land flow path. Zone (b) begins where the die channel increases from its smallest cross-sectional area and ends where the die channel no longer changes shape and defines the shape of the final extrudate. The average cross-sectional area of the redistribution channel is larger than the average cross-sectional area of the restrictive channel, but smaller than the average cross-sectional area of the land channel.

  In one embodiment, the redistribution channels increase symmetrically (flare up symmetrically) to the cross-sectional area of the final extruded composition that is cylindrical in shape. Instead, the redistribution channel can have a complex cross-sectional shape. One desired zone (b) has a cross-sectional area extending from the restrictive flow path outlet, one cross-sectional dimension is increased to form a rectangular cross-section, and its length (the length corresponds to the distance between the ends). At least a portion of a redistribution channel that includes a cross-sectional shape of a “bow-tie” or “dog-bone”. The “bow tie” portion distributes the polymer melt stream to a plate having a generally rectangular cross-sectional shape. The optimal parameters for zone (b) and the redistribution channel are highly dependent on the final article shape required for the restrictive and land channels. In general, the optimal redistribution flow path will gradually match the polymer melt flow from the restrictive flow path to the land flow path dimensions, as close as possible to a uniform flow rate across the land flow path. Change to shape. At the same time, the redistribution channel should be long enough to thermally degrade to an undesirable degree and not so long that the polymer melt is present in the die.

  Those skilled in the art will consider suitable redistribution channels based on the final extrudate cross section they desire to maximize the distribution of polymer melt stream and minimize the polymer melt residence time in the die. The channel shape can be designed appropriately and has been designed appropriately historically.

  Zone (b) is desirably a modular zone that allows replacement of components in zone (b) without having to replace components in zones (a) and / or (c). . One skilled in the art may wish to change only zone (b) when investigating different compositions of polymer melt. Different compositions may have different viscosities, for example, which may require changing the flow distribution profile in zone (b) to optimize the dimensional stability of the article. Like zone (a), zone (b) may itself contain a plurality of modular components.

Zone (c)-Land Zone Zone (c) is the final zone of the die and serves to stabilize the polymer melt to the cross-sectional dimensions of the final extrudate (before cooling of the final extrudate). Zone (c) tends to increase the dimensional stability of the final extrudate. The flow path in zone (c), ie the land flow path, remains essentially a constant cross-sectional shape throughout the length of zone (c). That is, the variation of any dimension of the land channel cross-sectional area at any two points in zone (c) (ie, the dimension perpendicular to the polymer melt flow) is within 5%, preferably within 2%, more Preferably it is within 1% and there may be no fluctuations. The land channel and zone (c) itself ends at the outlet orifice of the die through which the polymer melt exits the die. Zone (c) stabilizes the expansion of the polymer melt by directing the polymer melt stream parallel to the extrusion direction.

  The length of zone (c) is preferably such that the radial flow gradient (the difference in the flow rate of the polymer melt near the channel wall to the flow near the center of the channel) is minimized. It is sufficient to maximize the co-flow of the melt. To achieve this goal, the band (c) is typically 0.25 inches (6.35 mm) or more, preferably 0.5 inches (12.7 mm) or more, more preferably 1 inch or more (25 .4 mm) or more, more preferably 2 inches or more, more preferably 3 inches or more, and typically 10 inches (254 mm) or less, preferably 7 inches (178 mm) or less in length. Although these length values provide general guidance, the optimal length is best determined empirically for a particular polymer melt composition.

  The land channel may have any conceivable cross-sectional shape. For example, the cross-sectional shape may be a square, a rectangle, a rounded or chamfered rectangle, a circle, an ellipse, a star, a triangle, a hexagon, or an octagon. Particularly desirable shapes are wood boards (eg suitable as deck boards, trims or fascias), planks, bars, mandrels, railings (such as handrails with a curved top surface and a straight bottom surface and variations thereof. Profiled handrails), molded parts and spindles. The land channel desirably has a cross-sectional area within 10% of the cross-sectional area of the desired final extruded product.

  Desirable extruded products are known by square cross-sectional dimensions of 1 × 5/4, 2 × 4, 4 × 4, 2 × 6, 1 × 12, 3/8 × 12 and 2 × 2, and their dimensions. (For example, 2 is actually 1.5, 4 is actually 3.5, 6 is actually 5.5, and 12 is actually 11.5). is there.). However, the first number is the thickness in inches, and the second number is the width in inches.

  The one or more walls defining the land channel may include grooves or other shaping contours that extend substantially parallel to the length of zone (c). Such a forming profile is desirable to impart texture to one or more surfaces of the extrudate. For example, a groove that extends into one or more walls and extends in the extrusion direction may be useful to give the extrudate a grainy texture.

  The die of the present invention allows the craftsman to accurately and efficiently apply the extruder back pressure to achieve optimum filler mixing in the polymer matrix while minimizing thermal degradation of the polymer melt components. By being able to control, there are advantages over existing extrusion techniques. In particular, the die of the present invention allows the craftsman to polymerize when the filler and polymer matrix are generally incompatible, and when one or more of the filler or polymer is susceptible to heat degradation. The filler can be highly dispersed and uniformly distributed in the base material.

  As a further advantage, the die of the present invention provides a highly dispersed and uniformly distributed filler in the extruded polymer matrix while utilizing a compression ratio of less than 3: 1 and even less than 2: 1. Can be achieved. As a result, the base design is highly distributed and uniformly distributed in the polymer matrix with smaller flow path dimensions than required for a base that establishes a compression ratio of 3: 1 or greater. The manufacture of distributed filled polymer extrusion products is provided. Smaller channel dimensions are particularly advantageous when extruding products with a relatively large cross-sectional area. A 3: 1 compression ratio requires a die channel having a cross-sectional area at least three times the cross-sectional area of the die outlet orifice (ie, approximately the extruded product). Thus, the base may be inconveniently large for products with large cross sections to obtain a compression ratio of at least 3: 1. In particular, the die of the present invention can incorporate designs that produce compression ratios of 3: 1 or greater, but such compression ratios are highly dispersed and uniformly distributed in the extruded polymer matrix. It is not necessary for the base to achieve a distributed filler.

  1-4 show a typical base of the present invention.

FIG. 1 shows a plan cross-sectional view of a base 100 having a length L _D between an inlet end 103 and an outlet end 105 and defining a base channel 110. Outlet end 105 has a diameter D _D. Mouth ring 100 is comprised of lands band C having flow restriction zone A having a length L _A, flow redistribution zone B has a length L _B, and the length L _C. The flow restriction zone A defines a restrictive flow path 10 having an inlet orifice 12 (the inlet orifice 12 is also an inlet orifice to the base flow path 110) and an outlet orifice 14. The flow redistribution zone B defines a redistribution flow path 20 having an inlet orifice 22 and an outlet orifice 24. Land zone C defines a land flow path 30 having an inlet orifice 32 and an outlet orifice 34. The land flow path 30 has a width of W _C.

  The base 100 is modular and consists of a plurality of removable elements. Element 200 defines a flare up into restrictive flow path 10 and redistribution flow path 20. Elements 300, 350 (shown in FIG. 2) and 400 define a half-dogbone-shaped redistribution element in the redistribution channel 20. Elements 300, 350 (see FIG. 2) and 400 are attached to base 100 with bolts 500.

FIG. 2 shows a side cross-sectional view of the base 100 and shows a bolt 600 for attaching the base 100 to an extruder (not shown). FIG. 2 shows the height H _C of the outlet orifice 34 for the land channel 30. The exit orifice 34 is rectangular with W _C (shown in FIG. 1) larger than H _C (shown in FIG. 2). Also, the fact that the redistribution flow path 20 has a circular cross section at its inlet orifice 22 (shown in FIG. 1) and a rectangular cross section at its outlet orifice 24 is due to a comparison of FIG. 1 with FIG. it is obvious.

  FIG. 3 shows a cross-sectional view of the base 100 taken along the line AA, looking into the redistribution channel 20 facing the inlet end 105 (not shown). FIG. 3 shows a portion of the orifice corresponding to both the outlet orifice 14 of the restrictive flow path 10 and the inlet orifice 22 of the redistribution flow path 20. Element 300 has a curvilinear profile that extends into redistribution channel 20 to assist in redistributing the polymer melt.

  FIG. 4 shows a cross-sectional view of the base 100 taken along the line B-B looking towards the outlet end 105 and looking inside the redistribution channel 20. FIG. 4 also shows the land channel 30 and its outlet orifice 32 and outlet orifice 34 (which overlap in this view), as well as the modular component 400.

Extrusion Method The present method provides a means for extruding a polymer composition comprising a large amount of filler directly and efficiently into an article comprising a highly dispersed and uniformly distributed filler. It is an improvement of the method. This method provides a manufacturing method that combines and manufactures in one step, as opposed to multi-step methods of the current art (eg, methods of compounding filled pellets and then fabricating them into articles).

  When the macroscopic matrix is viewed with the naked eye, the filler is either when the majority of the filler particles are indistinguishable within the polymer matrix or appear to not aggregate with other filler particles. Is highly dispersed in the polymer matrix.

  If the flattened cross section of the composition appears to have a uniform distribution of filler to the naked eye observer (eg when visually inspected without magnification), the filler is evenly distributed in the polymer matrix. is doing. The strand process of US Pat. No. 5,516,472 produces a filled polymer composition having a weld line that delineates a clear strand over the flattened cross section of the polymer composition. The weld line constitutes a regular local region having a filler concentration that is lower than the average filler concentration in the composition, thereby ensuring a regular concentration of filler particles in the filled polymer composition. Consists of variation. Thus, the method of US Pat. No. 5,516,472 does not produce a filled polymer composition in which the particles are uniformly distributed in the polymer matrix.

  The filler may be hydrophilic or hydrophobic and may be organic or inorganic. Specific examples of the inorganic filler include clay, Portland cement, gypsum, calcium carbonate, and talc. The method of the present invention is particularly useful for extruding polymer compositions comprising a hydrophilic filler dispersed in a hydrophobic polymer matrix. The method is more particularly useful for the composition of cellulosic fillers (eg wood pulp, fibers, powders) in a hydrophobic polymer matrix. More particularly, 35% by volume or more, preferably 40% by volume or more, more preferably 45% by volume or more, and still more preferably 50% by volume or more filler (hydrophilic filler and talc) in the hydrophobic polymer matrix. Is useful to form a filled composition. Here, the volume% is based on the volume of the filled composition. In the method of the present invention, more than 50% by volume of a filler (including a hydrophilic filler and talc) is appropriately dispersed in a hydrophobic polymer matrix to form a filled polymer composition. Typically, it can contain less than 70% by volume of hydrophilic filler. However, the volume% is based on the volume of the filled composition. Here, the composition containing “a large amount of a filler” refers to a composition containing 35% by volume or more of a filler based on the amount of the composition material.

  The method of the present invention suitably incorporates any type of extruder (including single and twin screw extruders) in combination with the die of the present invention. Examples of the twin-screw extruder include a counter-rotating twin-screw extruder, a co-rotating twin-screw extruder, and a conical extruder. U.S. Pat. No. 6,450,429 discloses, for example, a twin screw extruder suitable for use in the present method. Conical twin screw extruders, particularly counter rotating conical twin screw extruders, are particularly desirable when dealing with heat-sensitive components such as cellulosic fillers. A conical twin screw extruder provides a higher degree of component mixing than a single screw extruder, but generates less heat than a standard twin screw extruder.

  Select a die having an inlet orifice that is similar in shape and size to the outlet orifice of the extruder to which the die is attached. Also, the back pressure is sufficient to ensure that the filler is evenly distributed within the polymer matrix but causes undesirable degradation of the polymer or filler in the extruder or zone (a). Select a zone (a) that provides a back pressure that is not as great. In order to design zone (a) with the appropriate length and channel cross section, the mixture viscosity, polymer melt flow, and known pressure drop and temperature models are used. Optimization with minimal empirical testing can provide those skilled in the art with the optimal parameters of band (a).

  In accordance with the above-mentioned teachings of the base, a base having a combination of zone (b) and zone (c) that will form an article with suitable shape and dimensional stability is selected.

  The die is attached to the extruder so that zone (a) is adjacent to the extruder, zone (c) is furthest from the extruder, and the flow path in the die is in fluid communication with the extruder outlet orifice. .

  The method of extrusion can follow known techniques, apart from the selection and use of the die of the present invention. Particularly desirable methods include a method for extruding wood flour filler in a polymer matrix (eg, US Pat. No. 5,516,472 (column 6, line 14 to column 9, line 15) and encapsulated. See U.S. Pat. No. 5,082,605 (in its entirety) utilizing wood flour fillers (apart from the base), which is hereby incorporated by reference. In general, a filler component and a polymer matrix component are fed into an extruder and heated and mixed to form a polymer melt, which is then extruded through a die to form a polymer matrix. An extrudate is formed containing the filler dispersed therein.

  The main component of the polymer matrix is a thermoplastic polymer, preferably a hydrophobic polymer such as polyethylene, polypropylene and polyvinyl chloride. Here, polyethylene refers to any homopolymer or a copolymer containing more than 50% polymerized ethylene units based on the total monomer units. Typical polyethylenes are low density polyethylene (LDPE) and high density polyethylene (HDPE). Similarly, polypropylene refers to homopolymers and copolymers containing more than 50% polymerized propylene units based on total monomer units. Particularly desirably, the polymers used as the polymer matrix in the process of the present invention are HDPE, polypropylene and polyvinyl chloride.

  Any filler is suitable for use in the present invention. The method is particularly useful for dispersing hydrophilic fillers in a hydrophobic polymer matrix. Hydrophilic fillers tend to resist dispersion in the hydrophobic polymer matrix and as a result tend to aggregate in the polymer matrix. The method is highly dispersed and uniform, even when using hydrophilic fillers in hydrophobic polymers, by providing a desirable balance of high temperature detrimental aspects (eg thermal degradation) and dispersion action. Enabling the formation of polymer compositions containing fillers distributed in the. Specific examples of typical hydrophilic fillers suitable for use in the present invention include cellulosic materials such as wood flour, wood pulp, wood fiber.

  Usually, the polymer matrix material is added to the extruder at the same time, immediately after, or simultaneously with, and thereafter the filler is added to the extruder. The filler can be added alone or in the form of a concentrate (eg, pellets containing filler encapsulated in a polymer matrix).

  In addition to the polymers and fillers for the polymer matrix, the method of the present invention includes additives such as lubricants such as metal stearates and fatty acid esters, inorganic fillers such as talc and calcium carbonate, coloring. Agent, UV stabilizers, biocides, fungicides, impact modifiers, reinforcing fibers (eg glass and wollastonite), hollow glass spheres, layered silicates, and coupling agents can be added. .

Filled polymer composition The method of the present invention can comprise a highly dispersed and uniformly distributed hydrophilic filler in a hydrophobic polymer matrix, a polymer composition comprising a large amount of filler. Extrudates can be produced. The filler may contain 35% by volume or more, 40% by volume or more, 50% by volume or more, and further 60% by volume or more of the filled polymer composition based on the volume of the filled polymer composition. it can. Preferably, the filler is a cellulosic material. More preferably, the filler is wood flour, wood pulp, wood fiber, wood flakes or any combination thereof. Most preferably, the filler is wood flour. The polymer is desirably polyethylene, polypropylene or polyvinyl chloride, preferably the polyethylene is HDPE. A polymer composition containing a large amount of one desirable filler contains wood powder that is highly dispersed and uniformly distributed in polyethylene and is extruded into the shape of a board.

  The composite material of the present invention has utility in, for example, deck materials, fence materials, and any applications where current wood boards, dowels, planks and bars are useful.

  The following examples serve to illustrate specific embodiments of the present invention. For each example, an 86 millimeter conical twin screw extruder (eg, Miraclon TC86) was used, and a Milaclon inlet adapter (also known as a universal adapter flange) was used to determine FIGS. A base similar to the base 100 in 4 is attached to the extruder. The universal adapter flange reduces the cross section of the extruder to the cross section of the inlet orifice of the die. For the description in FIGS. 1-4, the adapter flange is considered part of the extruder.

Example 1
The base has a length L _D of 16 inches (406 mm) and a diameter at its outlet end of 10 inches (254 mm). The length L _A of the flow restriction zone A is 1.4 inches (3.6 cm). The length L _B of the flow redistribution zone B is 10.6 inches (26.9 cm). The length L _C of the land zone C is 4 inches (10 cm).

The base has an inlet orifice 12 having a diameter of 1.57 inches (40 mm). The exit orifice 14 has a diameter of 0.75 inches (19 mm). The redistribution channel 20 extends symmetrically to a diameter of 1.5 inches (38 mm) before becoming rectangular. The land channel 30 has a width W _C of 5.50 inches (140 mm) and a height H _C of 0.94 inches (24 mm). Elements 300 and 310 reduce the height of redistribution channel 20 and are 3.3 inches (8.4 cm) in length. Elements 300 and 400 are centered in the width of the flow path and are symmetrical bulges with a maximum protrusion corresponding to a 4 inch (10 cm) wide portion of a 14.5 inch (36.8 cm) radius curve. Half the dog bone contour) protrudes into the redistribution channel 20. Element 350 does not protrude into the redistribution channel 20 except that it tapers to a uniformly narrower height across the width of the channel.

  The wood component is dried to 1 to 2% by weight moisture (wood component mass basis), then the ingredients in Table 1 are individually added to the feed section of the twin screw extruder at the indicated concentrations to form a filled polymer composition (Mass% is based on the total mass of the filled composition). To achieve a filled composition, the ingredients are mixed together in an extruder at a temperature of 350 degrees Fahrenheit (177 degrees Celsius). There is no need to pre-blend the wood component (60-mesh multi-pine) with the polymer component (HDPE).

  Fahrenheit at a flow rate of 850 pounds per hour (386 kilograms per hour) at a screw speed of 32 revolutions per minute to obtain an extrusion outlet pressure of 1950 pounds per square inch (13 megapascals). The filled polymer composition is extruded through a die while maintaining a temperature of 350 degrees (177 degrees Celsius). The resulting article is a 0.92 inch (2.3 cm) thick, 5.375 inch (13.7 cm) wide plate after cooling. The plate is free of visually visible unmixed component vortices when viewed from the flattened edge of the plate, with no visible aggregates of wood larger than about 1 mm.

  The base of Example 1 is an example of the base of the present invention having a compression ratio of 1.7. The compression ratio is again the ratio of the widest cross-sectional area of the mouth channel to the mouth outlet orifice. The method of Example 1 is an example of the method of the present invention that uses a die having a compression ratio of 1.7 to produce a uniform mixing of the cellulosic additive in the hydrophobic polymer matrix.

Example 2
Example 2 using the formulation and method of Example 1 except that the element 200 in the base is longer and larger than the element 200 in Example 1 and defines a restrictive flow path. To prepare. The different elements 200 are such that the length L _A of the flow restriction zone A is 5 inches (13 cm), the length L _B of the flow redistribution zone _B is 7 inches (18 cm), and the restricted flow. The base is changed so that the zone outlet orifice 14 has a diameter of 1 inch (25 mm).

  The base and method of Example 2 make a plate similar to that of Example 1. The base of Example 2 is an example of the base of the present invention, and the method of Example 2 is an example of the method of the present invention.

Comparative Example A
A filled composition is prepared using the same procedure, extruder and die as in Example 2, except that element 200 was removed from the die (thus omitting the flow restriction zone). The ingredients and concentrations in Table 2 are used to form the filled composition of Comparative Example A.

  As in Example 2, the wood component is dried to a moisture content of 1-2% by weight (wood component weight basis), and the components are individually added to the extruder to prepare a filled polymer composition. To achieve an extrusion outlet pressure (pressure at the extruder outlet orifice) of 1560 pounds per square inch (11 megapascals), using a screw speed of 32 revolutions per minute, 1013 pounds per hour (460 kilograms per hour) At a flow rate, the filled polymer composition is extruded through a die. The resulting 1 inch (2.54 cm) by 5.375 inch (13.7 cm) plate has visually apparent wood agglomerates of more than 1 mm of wood agglomerates and unmixed component vortices, and insufficient components Indicates internal mixing. Changing the extrusion temperature and speed does not remove agglomerates and vortices.

  Example 2 and Comparative Example A show that the flow restriction zone in the extrusion die is more highly dispersed in the filled polymer composition than the die without the flow restriction zone, increasing the extrusion outlet pressure. To produce a filled filler. The difference in composition formulation between Example 2 and Comparative Example A should not affect the extrusion outlet pressure or the degree of filler dispersion in the extruded plate.

  Example 2 further illustrates the method of the present invention using a die having a compression ratio of 1.7 that produces a uniform blend of cellulosic additives in the hydrophobic polymer matrix.

1 shows a cross-sectional plan view of one modular base of the present invention. FIG. 2 shows a side sectional view of the same modular base as in FIG. FIG. 2 shows a cross-sectional view of the die of FIG. FIG. 2 shows a cross-sectional view of the die of FIG.

Claims (20)

An extrusion die comprising a flow restriction zone (a), a flow redistribution zone (b) and a land zone (c), the extrusion die extending from one end of the extrusion die to the opposite end of the extrusion die Define the mouth channel,
(A) The flow restricting zone defines a restrictive flow path extending from the inlet orifice of the flow restricting zone to the outlet orifice at the opposite end, and the restrictive flow path has a cross-sectional area equal to (i) the smallest cross-sectional area of the mouth channel. Having an exit orifice and (ii) an average cross-sectional area less than the peripheral area at the restrictive flow path inlet end;
(B) the flow redistribution zone defines a redistribution flow path that extends from an inlet orifice adjacent to the outlet orifice of the restrictive flow path to an exit orifice at the opposite end of the flow redistribution zone, In fluid communication with the flow path, initially increasing the cross-sectional area from the cross-sectional area of the outlet orifice of the restrictive flow path, and (c) the land zone from the inlet orifice adjacent to the outlet orifice of the redistribution flow path A land flow path is defined that extends to an exit orifice at opposite ends, the land flow path is in fluid communication with the redistribution flow path, and any cross-sectional dimension variation at any two points between the inlet and outlet ends of the land zone. Is less than 5%,
The restrictive flow path has a smaller average cross-sectional area than the redistribution flow path or the land flow path, and the combination of the restrictive flow path, the redistribution flow path, and the land flow path defines the base flow path, From the inlet end of the base (the inlet end defines the restrictive flow path and the inlet orifice of the base) to the opposite outlet end (the outlet end defines the land flow path and the outlet orifice of the base), An extrusion die characterized in that it provides a laminar flow of coalesced melt.   The base channel through (a), (b), and (c) can only enter and exit by two openings (one at the inlet end of the base and the other at the outlet end of the base). The base according to claim 1.   The base according to claim 1, wherein the base includes at least one modular component.   The base of claim 3, wherein at least one of the flow restriction zone, the flow redistribution zone, and the land zone includes a modular component.   The base according to claim 1, wherein the base has a compression ratio of less than 2: 1.   The base according to claim 1, wherein the base has a compression ratio of at least 3: 1.   The mouthpiece of claim 1, wherein the flow restriction zone (a) has a length of 4 inches (10 centimeters) or less.   The base according to claim 1, wherein the restrictive flow path has a circular cross section at any point in the flow restriction zone.   9. A die according to claim 8, wherein the flow redistribution zone distributes the polymer melt from the restrictive flow path into the rectangular land flow path.   The die according to claim 1, wherein the land channel has at least one wall having a groove extending in an extrusion direction of the land channel.   The base of claim 1, wherein the restrictive flow path includes a static mixing baffle that allows laminar flow in the restrictive flow path.   The base according to claim 1, wherein the restrictive flow path has no static mixing baffle.   The restrictive flow path has a circular cross section, is 1-2 inches (2.5-5 cm) in length, and has an exit orifice of 0.5-1.5 inches (1.3-3.8 cm) in diameter. The base according to claim 1, characterized by having no static mixing elements.   A method for extruding a filled polymer composition comprising extruding a composition comprising a polymer and a filler from an extruder through an extrusion die, wherein the extrusion die is an extrusion die according to claim 1. A method characterized by that.   15. The method of claim 14, wherein the filler is selected from the group consisting of mica, talc and cellulosic material.   15. The method of claim 14, wherein the filled polymer composition comprises 40% by volume or more filler based on the total filled polymer composition volume.   The method of claim 16, wherein the filler is hydrophilic and the polymer is polyethylene or polypropylene.   The method of claim 17 wherein the polymer is high density polyethylene.   The process according to claim 14, characterized in that the extruder is a conical twin screw extruder.   The extrusion die has a restrictive flow path, the restrictive flow path has a circular cross section, is 1 to 2 inches (2.5 to 5 cm) in length, and has a diameter of 0.5 to 1.5 inches. 15. A process according to claim 14, characterized in that it has an exit orifice (1.3 to 3.8 cm) and is free of static mixer elements.

Images